nasanov/vision-trainer-pattern-generator ? reverse-engineered prompt

Build me a web app for making vision training letter patterns that I can use right in the browser and print on A4 landscape pages.

I want to be able to generate a random grid of letters, optionally include numbers, control how many rows and columns there are, choose whether duplicates are allowed, and quickly regenerate new patterns. Let me customize the look too, like font size, font family, and text color, and give me an option to show or hide a light alignment grid and a center fixation point.

It should also let me drag individual letters around and edit their styling if needed, then save those settings as presets in the browser so I can load them later. Please include PDF export for multiple pages, around 1 to 30, with a progress indicator while it generates, and make sure each page gets a different random pattern. Also add a simple print button for the current layout. If you need anything unclear, look up current docs online first.